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The basic concept of superconductive magnetic gears (SMGs) is to maximize the benefits and impact of the magnetic gearing technology by highlighting the future perspective of SMGs to produce a more efficient and compact system. This paper deals with a new analytical method (AM) for the calculation of magnetic field distribution in an SMG. A 2-D AM based on Laplace's partial differential equations of magnetic scalar potential in the different subdomains of a magnetic gear is introduced and solved by considering the corresponding boundary conditions. The proposed method shows a significant reduction in the consumed calculation time compared with the finite-element method (FEM) and can be used as a basis for design optimizations. Two-dimensional AM results are compared against those obtained from 2-D FEM simulations, using an accurate, yet efficient, high-temperature superconductor (HTS) modeling, yielded by a detailed localized E-J power law approach combining the different aspects of HTS in a numerical method, so as to find out the benefits and validity of the presented AM. Finally, the effects of PMs and pole pieces' dimensions on torque density are realized. [ABSTRACT FROM AUTHOR]

In this paper, the high temperature superconductor (HTS) winding and multitoothed structure are newly incorporated into the doubly salient (DS) and flux-switching (FS) machines, leading to create two new magnetless machines, namely the HTS-based multitoothed switched reluctance (HTS-MSR) and HTS-based multitoothed flux-switching (HTS-MFS) machines. Consequently, the design equations of the three machines, namely the MSR, HTS-MSR, and HTS-MFS, are formulated. The corresponding performances are analyzed by using the time-stepping finite element method (TS-FEM). By utilizing both torque-producing zones, the two HTS-based machines can achieve better performances than the MSR one. Moreover, the HTS-MFS can offer higher torque density than the HTS-MSR, but associated with larger torque ripple. [ABSTRACT FROM PUBLISHER]

The Karlsruhe Institute of Technology (which is a merger of former Forschungszentrum Karlsruhe and Karlsruhe University) is responsible for the design, construction and testing of the high temperature superconductor (HTS) current leads for the stellarator Wendelstein 7-X (W7-X) which is presently under construction at the Greifswald branch of the Max-Planck-Institute for Plasma Physics. The current leads are of the binary type, the HTS part covering the temperature range between 4.5 K and 60 K while the heat exchanger covers the range between 60 K and room temperature being cooled by 50 K He. In total 2 prototypes and 14 series current leads are required with a nominal current of 14 kA and a maximum current of 18.2 kA. The paper describes the design and first test results of the prototype HTS current leads. [ABSTRACT FROM AUTHOR]

In this paper, a novel coaxial magnetic gear (CMG) using bulk high temperature superconductors (HTS) is proposed. By substituting bulk HTS for ferromagnetic material, a novel stationary ring is resulted, which can not only provide the desired field modulation effect but also suppress the end-effects that commonly occurred in the traditionalCMG. The performance of the proposed bulk HTSCMGis assessed and then verified by using finite element analysis. [ABSTRACT FROM AUTHOR]

This paper presents a new synchronous motor whose stator uses 2 High Temperature Superconducting (HTS) pancake-coils wound from 2G HTS tapes and 4 conventional copper coils, while the rotor contains 75 buLk HIS elements. All superconducting materials are cooled by liquid nitrogen (77 K). The HIS and copper armature includes 3 phase circuit and is mounted in the slots of a nonmagnetic and insulating material. Each phase winding, fabricated in the form of a pancake-coil, is distributed in slots of 60-degree intervals. YBCO melt-textured pucks were incorporated into the rotor and the reluctance was tested. In addition, a unique cooling system using a copper conductor is designed, which is similar to that of a superconducting flywheel. Finally, we present and analyse results on measuring DC critical current and self-field AC loss in HIS tape supplied by American Superconductor. The measurement systems are described. The results on the AC loss measurement of YBCO samples are presented and analyzed within the framework of the critical state model. [ABSTRACT FROM AUTHOR]

The metal organic deposition (MOD) of YBCO High Temperature Superconducting films on RABiTS (Rolling Assisted Biaxially Textured Substrates) templates has been developed at American Superconductor as a low-cost, scalable manufacturing process for the commercialization of the Second Generation (2G) HTS wire. The MOD process is based on the deposition of a trifluoroacetate (TFA) based metal organic precursor film which is converted, in an ex-situ process, to the superconducting YBCO film. A major goal of the development has been achieving high critical currents. This paper reports the preparation and characterization of MOD-YBCO films with critical currents exceeding 500 A/cm-w (77 K, self-field) using a scaleable thick film approach on RABiTS templates. The high critical current films were obtained through optimization of the precursor composition, nucleation and growth conditions. The through-thickness dependence of the critical current density of MOD films as a function of film thickness and a correlation of the through-thickness transport properties and microstructure of the thick MOD/RABiTS samples is reported. [ABSTRACT FROM AUTHOR]

An 8 MVAR, 13.8 kV Superconducting Dynamic Synchronous Condenser (SDSC) prototype was tested on the Tennessee Valley Authority (TVA) grid for about a year. It shared a bus with an arc furnace. The SDSC was subjected to transient currents and harmonics created by the arc furnace, which consisted of up to 50 % negative sequence and 20% zero sequence components. The SDSC operated successfully in the presence of such high transient/harmonic currents. It provided cycle by cycle correction of voltage during operation. The benefits of voltage correction were observed both at the local bus and at the generator bus of a power generation station several miles away. Currently two commercial units rated 12 MVAR, 13.8 kV, are on order by TVA and are scheduled for delivery in December 2006 and March 2007. These units will be skid-mounted for easy installation on site. This paper discusses test results of the prototype unit operation on the grid and describes its potential applications for voltage support in wind farms. [ABSTRACT FROM AUTHOR]

When a synchronous generator connected to the power grid experiences a fault, it is required to stay on line, ride through the fault, and be able to carry full rated field current when the fault is cleared. The peak current during these events could be 2 times higher than the normal operating current. This may cause an HTS rotor coil to go into normal state and generate Joule heating. If the fault event is short enough and the heat dumped can be carried away by the cooling system, the coil may recover to the superconducting state at the end of the fault. Otherwise, the coil may thermally run away, or ‘quench’. To investigate the quench behavior of the HTS rotor coil of the 100 MVA generator at GE Global Research Center, a 1.5 MVA prototype coil was developed and tested to quench under different conditions. The experiment design, set up, tests and test results are presented in this paper. [ABSTRACT FROM AUTHOR]

For the superconducting magnet system of the International Thermonuclear Experimental Reactor, ITER, 60 current leads for a total current of more than 2500 kA are needed. To reduce the resultant large refrigerator load at 4.5 K, High Temperature Superconductor current leads (HTS-CL) could be used. Therefore, EFDA CSU Garching had launched a development program for a 70 kA HTS-CL demonstrator. The Forschungszentrum Karlsruhe and CRPP developed and built this CL optimized for 50 K Helium operation. In 2004, the CL was successfully tested in the TOSKA facility at the Forschungszentrum Karlsruhe. The very encouraging results lead to testing this CL with 80 K Helium because ITER provides a large 80 K Helium cooling capacity for the thermal shields. At the end of last year, the test could be successfully performed demonstrating that high current capacity current leads can be stably operated at about 80–85 K. Recently, the CL was retested using liquid nitrogen which would be an interesting alternative option. In this paper, the test results for the 80 K He cooling operation as well as for the operation with LN2 are presented and compared to the results obtained before for nominal conditions. [ABSTRACT FROM AUTHOR]

SuperPower, Inc. and Nexans SuperConductors GmbH have partnered to develop a superconducting fault current limiter for transmission level applications. The device employs SuperPower's Matrix Fault Current Limiter (MFCL) technology and BSCCO-2212 bulk material manufactured by Nexans' melt cast processing technique. The development program has been underway since June 2002 and is divided into a series of prototype demonstrations of progressive capability, culminating in a Beta prototype that will be installed at a host utility on a 138 kV line. This paper describes the test results of the first major program milestone, a proof-of-concept prototype at distribution level voltage. The test results show the expected current limiting performance of the MFCL technology to provide fast current limiting and dynamic resistance development before the first peak of the fault. The fault current evenly distributes among the elements of the MFCL array, which employs a resistive-inductive approach for limiting the current. The results also show the excellent electric field performance of the BSCCO-2212 material. [ABSTRACT FROM AUTHOR]

In the frame of the European Fusion Technology Programme, the Forschungszentrum Karlsruhe and the CRPP Villigen have designed and built a 70 kA current lead for the ITER TF Coils using High Temperature Superconductors (HTS). At the beginning of 2004 the HTS current lead was installed and tested in the TOSKA facility of the Forschungszentrum Karlsruhe. The scope of the experiment was to characterize the current lead in steady state conditions and to explore the operation limits as well. For this, the temperature profile, the contact resistances, the heat load at 4.5 K, the required 50 K He mass flow rate, and the temperature margin were evaluated. The safety margin in case of a loss of He mass flow was studied, too. The paper describes the experimental results as well as the thermal and electrical models developed. [ABSTRACT FROM AUTHOR]

Technologically, the most advanced conductor utilising high temperature superconductors is the multifilamentary tape produced by the powder in tube method. Previous investigations have indicated that the filaments in these materials are strongly connected by superconducting paths. This connectivity is of particular importance in, amongst other things, governing the dissipation of the conductors when carrying AC currents or exposed to varying magnetic fields. In this paper we report direct measurements of the transverse (in contrast to the more usual longitudinal) current carrying capability. Measurements of electric field versus current ('E-I characteristics') for transverse and longitudinal transport currents as a function of applied magnetic field and temperature are reported. Our data indicates that the filaments are indeed strongly connected by superconducting paths but also that the E-I characteristics for the transverse and longitudinal connections are different. [ABSTRACT FROM PUBLISHER]

This paper reports a study on the fabrication technology of high performance functional devices, where high temperature superconductor and compound semiconductor devices are monolithically integrated on the same substrate. We investigated optimal conditions for epitaxial liftoff process and succeeded in fabricating HTS device and GaAs MESFET on SrTiO/sub 3/ substrate without degrading characteristics of superconductor and semiconductor devices. We also carried out basic integrated circuit fabrication processes such as patterning and etching for quasi-monolithic structure. The results confirmed that fabricating high performance functional devices is feasible. [ABSTRACT FROM PUBLISHER]

The use of melt processed YBCO in permanent magnet applications requires the calculation of magnetic fields in the interior of superconductors. Although the Bean model can be used, analytic solutions are only available for simple shapes and numerical methods are required for most cases. In this paper, the technique of adjusting the boundary between current carrying and current free regions to ensure zero field within the boundary is used, in combination with the Kim model for Jc. The results are applied to discs being magnetised in a uniform field and trapping fields after saturated magnetisation. It was found that a good approximation can be obtained by using a constant Jc of the value at half the applied field instead of the Kim model. This may be of great importance for the practical applications of melt processed YBCO permanent magnets. [ABSTRACT FROM PUBLISHER]